The invention is generally related to systems and methods for control over the delivery of medication and more particularly, to a safety system for monitoring and controlling the delivery of medication.
Diabetes is a metabolic disorder that afflicts tens of millions of people throughout the world. Diabetes results from the inability of the body to properly utilize and metabolize carbohydrates, particularly glucose. Normally, the finely-tuned balance between glucose in the blood and glucose in bodily tissue cells is maintained by insulin, a hormone produced by the pancreas which controls, among other things, the transfer of glucose from blood into body tissue cells. Upsetting this balance causes many complications and pathologies including heart disease, coronary and peripheral artery sclerosis, peripheral neuropathies, retinal damage, cataracts, hypertension, coma, and death from hypoglycemic shock.
In patients with insulin-dependent diabetes, the symptoms of the disease can be controlled by administering additional insulin (or other agents that have similar effects) by injection or by external or implantable insulin pumps. It is understood that throughout this document, the terms “patient” and “user” are used interchangeably. The “correct” insulin dosage is a function of the level of glucose in the blood. Ideally, insulin administration should be continuously readjusted in response to changes in glucose level.
Presently, systems are available for monitoring glucose levels by implanting a glucose sensitive probe into the user. Such probes measure various properties of blood or other tissues, including optical absorption, electrochemical potential and enzymatic products. The output of such sensors can be communicated to a hand held device that is used to calculate an appropriate dosage of insulin to be delivered into the blood stream in view of several factors, such as a user's present glucose level, insulin usage rate, carbohydrates consumed or to be consumed and exercise, among others. These calculations can then be used to control a pump that delivers the insulin, either at a controlled “basal” rate, or as a “bolus.” When provided as an integrated system, a continuous glucose monitor (“CGM”), a pump, and a control means work together to provide continuous glucose monitoring and insulin pump control. The components of integrated diabetes management (“IDM”) systems, whether implemented as a fully closed-loop, semi closed-loop, or an open loop system must be tightly integrated to insure the accuracy of the glucose monitor and to protect the user from either under- or over-dosage of insulin, as well as improved usability, control, and safety of the system.
Not all components are likely to be made by a single developer or be based on a universal design platform, and users have always tended to mix and match components to suit their individual needs. In the case of a development platform for these systems, it is likely that both outside-designed (third-party) controller modules as well as insider-developed systems and platforms may evolve over time, and more than one version may exist at any given time. While modern trends often promote hardware and software compatibility, when mixing components created by different designers or manufacturers, one must consider the careful design of hazard mitigation features, such as the safety limits of such critical life-saving devices and components. As hardware and software components get replaced or improved, it is possible that many aspects of hazard mitigation becomes so coupled with the particular configurations of a particular case, that a careful redesign may be necessary to account for the new changes. Moreover, it is anticipated that system and value constraints can change due to component hardware and software upgrades over the life of a closed loop or semi-closed loop diabetes control system.
Under normal operating conditions, a fully autonomous closed loop system is in full control of its insulin command calculation. This implies that while closed loop is in effect, the user may be denied access to some of the system's functionality such as the ability to deliver a bolus. While, in some instances, this may have been designed from a safety perspective, the user may perceive such features to inhibit control over the ability to self-medicate or limit control over the device. Consequently, a closed loop or semi-closed loop system should be able to account for the effects of a user-initiated command such as a meal bolus, even if it is not necessarily accompanied with meal content information. Yet, the requirement to allow such user intervention could cause a momentary violation of pump delivery limits set by designers, even if the control system (without the addition of the invention herein disclosed) was designed not to generate autonomous commands that exceed the same pump delivery limits.
What has been needed, and heretofore unavailable, is an integrated, automated system combining continuous glucose monitoring and controlled insulin delivery that provides modularity for rapid development of system components by different designers, and that bestows an increased sense of freedom to the user, such as the ability to self-medicate in conjunction with a closed-loop system, all while providing for safety in the accurate delivery of insulin.